MW

Checking out a new lens from B&H. Sigma 70-300mm for Nikon. I was comparing autofocus using the viewfinder vs live view. The camera body is a D5100. Focus is OK. However, the exposure through the viewfinder looks about 1/2 stop over exposed compared to live view. Camera was locked in position. The live view looks like the correct exposure when compared to same scene is of a different lens. Same experiment with a different lens does not result in an exposure difference-- LV vs viewfinder.

PS- I kept the viewfinder covered when my eye was not against it.

Questions. Is there an obvious explanation? Is the lens defective? Anything else I should test out?

CatMarley Loc: North Carolina

I don't understand the question. Are you comparing photos taken using live view versus one taken using the optical viewfinder, or are you comparing the brightness of the optical viewfinder to the liveview screen? Remember that the viewfinder is what the mirror is bouncing to your eye directly with the light from the subject and the liveview screen is an electronic image. They are NOT going to be the same. You can tweak them to look somewhat the same by changing the brightness of your liveview screen. If the photos are different, you may have a light leak from the optical viewfinder when using liveview.

MW

I am comparing photos. The brightness of the optical viewfinder vs the LCD is not the issue. That's why I used the word "exposure" which pertains to a captured image. (I would not expect the viewfinder and LCD screen to look alike in any case.)

MW

Additional data: Metering mode doesn't make any difference. Metadata tells me that the difference is shutter speed in Aperature priority (not surprising). I need to check S and P. In manual there is no difference in exposure.

Again- the issue is that with the camera locked in position, auto exposure calculates a different solution depending on whether the optical viewfinder or live view is used. Before anyone asks- I am careful to keep light from entering at the eyepiece. And other this does not happen with other lenses.

zundapp5 Loc: Portugal

Here you can find an answer; http://www.dpreview.com/forums/thread/3375056

BboH Loc: s of 2/21, Ellicott City, MD

If I recall correct;ly, thru the ViewFinbder you are seeing the scene as your eye would. With LiveView you see the scene with the camera settings.

rjriggins11 Loc: Colorado Springs, CO

Just adjust the LCD brightness to match the viewfinder and then adjust your compensation to your liking. That's what the Pro's do.

MW

And this will correct the overexposure of photos taken using the optical viewfinder while not changing the exposure of those taken using live view?

MW

Clarification: I'm NOT talking about the relative brightness of the viewfinder vs the LCD.

When I used the word "exposure" I was referring to photos actually taken. It did not occur to me that "exposure" might refer to anything else.

Morning Star Loc: West coast, North of the 49th N.

Just like there are differences in computer monitors (that's why you calibrate them), I would expect differences between optical viewfinder and live view. To get the best possible image, you will probably have to combine what your eyes see in the viewfinder or on the LCD screen, with what the camera tells you about the image in 'info'.



No, this would not be enough to make me think the lens is defective. Try taking a photo using the optical viewfinder, so it looks best to your eye. Then take a photo with the same lighting and composition, using the LCD screen, or 'live view' but also adjusting your settings so it looks best to your eye. Compare the prints (or the images on your computer screen) side-by-side. Also compare the exif data between the two photos. That will tell you which of the two will give you better results, or where you need to make adjustments.

twillsol Loc: St. Louis, MO

I am puzzled. The camera will take the same picture, no matter how you use it. If you look at live view and then take the image, it should be the same as looking through the viewfinder and taking the picture; Unless you are changing the settings depending how you look at it. Maybe, I do not understand your question???

MW

Check out the link, above, provided by zundapp5. That is exactly what is going on in my case. Maybe that will be clearer than my description. The wierd part is that it is only happening with one particular lens. With all others (Nikons) all this glitch does not occur. Also note that it only occurs in aperature priority mode. I'm concluding for now that there is an issue in the interface between the Sigma lens and the Nikon body that huggers the metering when "A" aperature priority is selected.

The metadata shows that a shutter speed about twice as long is calculated and used for the photo taken when the optical viewfinder is used as when live view is used. That is the only difference between how the photos were taken.

At least there is a work around in that I can use Program mode and override the aperature selection. It functions virtually like aperature prioryy when used thusly.

MW

Its clear that the behavior is so weird that some readers are having trouble getting their heads around what I'm describing. But that's what is actually happening. My first reaction was "huh" as well. I had to repeat the test about a dozen times before I accepted that want some goofy I was doing.

LFingar Loc: Claverack, NY

Barring light leakage through the viewfinder, which you have eliminated, there has to be some difference in how the camera measures light levels using the 2 different viewing methods. Is there any possibility that one viewing method defaults to a different exposure method without you knowing it? What does your exif data show? It would seem to me that the camera has to be doing something different in the 2 situations.

MW

The EXIF data shows that when using the optical view finder the shutter speed is slower by about half. Example the correct exposure (LV) in one example was 1/250 but the exposure with optical viewfinder was 1/125. It is not always exactly x2 but that is typical.

Remember this is in aperture priority so the EXIF shows identical ISO and f-stop. Only shutter speed changes. The actual image agreed with the EXIF data recorded.

I've just submitted an inquiry to B&H to ask if this is a known issue and if I should return the lens. They may tell me to contact Sigma directly. The lens is actually usable in all other modes and you can use "P" (Program) in a way that pretty much duplicate Aperture priority. Given that and given that it's a pretty inexpensive lens anyway I don't want the hassle of return and replacement if I'm likely to get an identical replacement with the same behavior.

My first thought was that what I was seeing was impossible but then I realized that it's probably a case of firmware talking to firmware so unexpected bizarre behavior is not unreasonable.